Stencil printing machine

ABSTRACT

A silk screen printer includes a printing table, a stencil held in a frame, and a squeegee which is movable relative to the frame to enable a first pattern on the stencil to be transferred to print material registered on the printing table in order to form a second pattern. During an actual printing sequence, the squeegee is intended to move over the stencil and relative to the frame in a first direction, whereas the stencil and the stencil-frame are intended to move in another direction opposite to the first direction. The printing table is a flat printing-table, which can be displaced synchronously with the frame. During a printing sequence, a gripper operative to collect print material located in a laying-on station is registered to the printing table for movement in common therewith.

TECHNICAL FIELD

The present invention relates to a silk screen printer and moreparticularly to a silk screen printer of the kind which comprises aprinting table, a frame-held stencil, and a squeegee which can bedisplaced relative to the stencil frame, such that a first patternformed on the stencil can be applied to print material registered in aprinting position on said table and therewith form a second pattern onsaid material, by forcing ink, paste, lacquer or varnish through apattern of holes formed in the stencil and corresponding to said firstpattern, with the aid of said squeegee.

The invention is concerned particularly with silk screen printers of thekind in which the printing table is flat and functions to support thinmaterial to which the second pattern is to be applied.

Although the printer is constructed to print thin material, it will beunderstood that the printer is also able to print thick and stiffmaterial, provided that said material can be held firmly by grippersprovided therefor.

BACKGROUND ART

Various silk screen printer of this kind are known to the art. Inaddition to endeavours to increase the printing speed of such printers,endeavours have also been made constantly to enable the second patternto be applied to print material with no positional discrepancy or withonly a small positional discrepancy.

The demand for high printing speeds, e.g. speeds in excess of 1500prints per hour, is normally counter-active to the demand for smallpositional discrepancies.

An example of one known printer equipped with a flat printing table withwhich a high printing speed is desired and where discrepancies can bekept low is described and illustrated in U.S. Pat. No. 4,516,495.

In view of the measures taken in the development of the presentinvention, mention should perhaps also be made to U.S. Pat. No.3,874,289, and particularly to FIGS. 8 and 9 of this specification,which teaches a silk screen printer which lacks a flat printing tablebut in which measures have been taken to cause the squeegee to move overthe stencil and relative to the stencil frame in a first directionduring an actual printing sequence while the stencil and stencil-frameare arranged to move in a second direction opposite to said firstdirection. The second direction coincides with the speed and directionof the movement of a flat and/or an angled object. It can be assumedthat the speed of the object in relation to a stand which forms part ofthe silk screen printer is synchronized with the speed of the stencilframe relative to said stand.

SUMMARY OF THE INVENTION Technical Problems

A study of the present standpoint of techniques as described above willshow that in the case of a silk screen printer equipped with a flatprinting table, a frame-carried stencil, and a squeegee which can bemoved relative to the stencil-frame, a qualified technical problemresides in the ability to create, with the aid of simple means,conditions which will enable movement of the squeegee, the length ofsqueegee movement, and the length of stencil or stencil-frame movementto be reduced, so as to enable the printing speed of the printer to beincreased drastically as a result of these shorter distances.

It will also be seen that a technical problem resides in the provisionof a silk screen printer equipped with a flat printing table andintended for printing relatively thin material with which the aforesaidproblem has been solved and therewith provide a simple grippingarrangement and a simple movement of print material from a laying-onposition to a printing position and from a printing position to alaying-off.

Another technical problem associated with a silk screen printer of theaforesaid kind equipped with a flat printing table is one of realizingthe advantages that can be gained when the printing table is able tomove reciprocatingly in synchronism with the stencil and stencil-frame,and also of realizing that the gripper means need not be registeredrelative to the printing table solely in a known manner, but canaccompany the printing table in its direction of movement during theprinting sequence, and in other respects adapt the path of movement andspeed of the gripping means to the aforesaid conditions.

It will also be seen that a further qualified technical problemassociated with a silk screen printer having a flat printing table andintended to solve one or more of the aforesaid technical problems is oneof realizing the significance of utilizing a printing table which can beraised and lowered, in a manner known per se, and which during aprinting sequence can be moved to an upper position such as to bring agripper in a registered position when raised.

It will also be seen that a qualified technical problem is one ofrealizing the advantage of using known raisable and lowerable grippers,of which one gripper is intended to take an upper position when printmaterial is intended to pass over the printing material to a materialand gripper registering position, and then lowered to a registeringposition in coaction with the printing table.

It will also be seen that a technical problem associated with the use ofa number of grippers related to one another via endlessmovement-transmission means, such as chains or the like, is one ofrealizing the advantage that can be gained by using said grippers andsaid transmission means in a known manner, such that said grippers andtransmission means will move intermittently and therewith enablesimultaneous registration of a first gripper in the laying-on positionand registration of a second gripper relative to the printing table orstand in the printing position, and to afford coaction between grippersand printing table such that the gripper will finally be registered whenthe printing table is raised to its upper position.

Finally, it will be seen that a qualified technical problem is one ofrealizing the advantage that is gained when the movement path of thesqueegee relative to the stand and the movement paths of thestencil-frame relative to said stand are of equal length and adaptedparticularly to the length dimension of the printed pattern in themovement or transport direction.

Solution

The present invention affords a solution to one or more of the aforesaidtechnical problems and said qualified technical deliberations, departingfrom a silk screen printer which incorporates a printing table, aframe-held stencil, and a squeegee which is movable in relation to saidstencil-frame, such as to enable a first pattern formed on the stencilto be transferred, in the form of a second pattern, onto print materialregistered in position on the printing table, said material being sothin as to make it preferable for said material to rest on the printingtable during the actual printing sequence.

The invention utilizes the principles applied in another basicsilk-screen printer construction, namely that the squeegee shall bearranged for movement over the stencil and relative to the stencil-framein a first direction during the actual printing sequence, while thestencil and stencil-frame are arranged to move in another directionopposite to the first direction.

With the aforesaid combination of features taken from a silk screenprinter having a flat printing table and a silk screen printer adaptedto print directly onto flat or right-angled objects, the presentinvention provides a unique coordination of printer features where theprinting table is a flat printing-table and is reciprocatingly movablesynchronously with the frame, and where grippers which collect printmaterial from a laying-on position are registered with the printingtable or printer stand for movement common therewith during the printingsequence.

According to one further embodiment of the invention, the printing tableis capable of being raised and lowered and is intended to take an upperposition during the printing sequence.

It is also proposed that the grippers can be raised and lowered andarranged to take an upper position when print material is intended topass over the printing table to a material-and-gripper registeringposition.

According to a further embodiment of the invention, the speed at whichthe squeegee is able to move in relation to the stencil is twice as fastas its movement relative to a printer stand.

It also lies within the concept of the invention to relate a pluralityof grippers one to the other, via endless movement-transmission means,such as chains, and to move the same intermittently, therewith enablingsimultaneous registration of a first gripper in the laying-on positionand registration of a second gripper in the printing table, this latterregistration preferably being effected when the printing table is raisedto its upper position.

Finally, the movement path of the squeegee relative to the printer standand the movement path of the stencil-frame relative to said stand are ofequal distance and are preferably adapted to the length extension of theprinted pattern in the transport direction.

Advantages

Those advantages primarily afforded by an inventive silk screen printerreside in the possibilities of enabling a silk screen printer having aflat printing table to produce print at a speed which considerablyexceeds the speed normally attainable with conventional silk screenprinters having flat printing tables. It is expected, in this regard, toachieve an increase in printing speeds of more than 30%, and with normalprinter sizes generating prints in the order of 70×100 cm, the inventiveprinter is able to achieve a printing capacity of above 2000 prints perhour.

Theoretical calculations indicate that the printing speed can beincreased to values of between 50 and 80%.

The primary characteristic features of an inventive silk screen printerare set forth in the characterizing clause of the following Claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail with reference to twoexemplifying embodiments at present preferred and lying within the scopeof the present invention, and also with reference to the accompanyingdrawings, in which

FIG. 1 illustrates highly schematically a first embodiment andillustrates the end of a printing sequence, with stencil, printmaterial, gripper and printing table in a terminal position of aprinting sequence;

FIG. 2 illustrates subsequent and necessary raising of the squeegee;

FIG. 3 illustrates subsequent and necessary raising of the squeegee,frame and stencil in the form of a unit, and simultaneous lowering ofthe printing table;

FIG. 4 illustrates a later position or state, in which print-materialplaced in the laying-on position by means of a gripper has beendisplaced between stencil and printing table, which have been caused tocarry out a return movement during displacement of said print material;

FIG. 5 illustrates a following position of the squeegee, frame andstencil in positions coacting with the print material and with with theprinting table in an upper position so as to enable a printing sequenceto commence;

FIG. 6 illustrates an operational state during an ongoing printingsequence immediately before reaching the operational state illustratedin FIG. 1; and

FIG. 7 illustrates a second embodiment of a silk screen printer withstencil-frame, print material and printing table in the operationalposition shown in FIG. 1.

DESCRIPTION OF EMBODIMENTS AT PRESENT PREFERRED

The following description is primarily intended to illustrate thefunction of a silk screen printer having a flat printing table andoperating in accordance with the principles of the present invention,said description being made with reference to FIGS. 1-6 of theaccompanying drawings. In order to simplify the drawings, the devicesand constructional elements required for moving the squeegee, raisingand lowering the frame, raising and lowering the printing table inrespective displaced gripper-bars and for registering the same inrespective registering positions have not been shown.

Mention will be made, however, in the following to those publications inwhich examples of such devices and constructional elements areillustrated.

Thus, as illustrated in FIG. 1, the present invention is based on a silkscreen printer 1 which comprises a flat printing table 2, a stencil 4stretched in a frame 3, and a squeegee 5 which is movable in thedirection of arrow "A" relative to the frame 3 and the stencil 4, suchas to transfer a first pattern on the stencil onto print material 6registered in a printing position on the printing table 2, so as to forma second pattern on said print material. The frame 3 and the stencil 4are arranged for movement in the direction of the arrow "B".

FIG. 1 also illustrates a first gripper 7 which is operative to hold theprint material 6 during a printing sequence and which, in theillustrated position, is registered relative to a printer stand 9 or tothe printing table 2.

In the position illustrated in FIG. 1, a second gripper 8 is operativeto grip print material 6a located in the laying-on station.

The grippers 7 and 8 can be moved in unison to the left in FIG. 1, inthe direction of the arrow "C", by an endless movement-transmissionmeans, in the form of a chain 10. The gripper 8 is also registeredrelative to the stand 9 in the position illustrated in FIG. 1.

Any appropriate arrangement can be used for effecting movement of thegrippers and for registering said grippers in position. An example ofone such arrangement is described and illustrated in U.S. Pat. No.4,221,165, FIGS. 1 and 1A.

FIG. 1 illustrates the mutual positions of the printing table 2, theframe 3, the squeegee 5, the print material 6 and 6a, and the grippers 7and 8 at the end of a printing sequence, and the direction arrows "A","B" and "C" indicate the movement of these printer members prior to theoperational state of the printer illustrated in FIG. 1.

It should be noted that the various operational states of the printerillustrated in FIGS. 1-7 have been shown in a following sequence, so asto provide a clearer understanding of the mutual positions ofdisplacement of the printer members.

As illustrated in FIG. 2, at the end of a printing sequence the squeegee5 is raised, so as to release coaction of the stencil 4 with the printmaterial 6, thereby enabling the print material 6 to be removed from theprinting position and also to enable the print material 6a located onthe laying-on station to be moved to the printing position by means ofthe gripper 8.

FIG. 3 illustrates the operational state of the printer immediatelyafter the operational state illustrated in FIG. 2, and the arrow "D"indicates that the frame 3, together with the stencil 4, and thesqueegee 5 have been raised to a position in which print material andgripper are able to pass freely therebeneath.

The reference sign "E" indicates that the flat printing table 2 is, atthe same time, caused to take a lower position, so as to enable freepassage of the gripper 8 and further print material 6a immediately abovethe printing table, to the material printing position.

With particular reference to the positions of the printer membersillustrated in FIGS. 1 to 3, FIG. 4 shows that the frame 3, togetherwith the stencil 4, is then displaced horizontally in the direction ofthe arrow "F", somewhat to the right, at the same time as the squeegee 5is displaced horizontally to the left through an equally long distancefor refilling purposes, as indicated by the arrow "G".

The arrow "H" illustrates that the flat printing table 2 is alsodisplaced horizontally to the right. This displacement of the printingtable 2 and the frame 3 (together with the stencil 4) takes placesynchronously through the intermediary of an arrangement not shown.

At the same time as the frame 3 and the printing table 2 are displacedhorizontally to the right, the gripper 8 is displaced to the left, so asto take the position illustrated in FIG. 4 and therewith place the printmaterial 6a in the printing position.

It should be noted that the gripper 12 does not grip print material inthis position, since new print-material shall be gripped by the gripper12 when the gripper is registered.

The arrow "J" in FIG. 5 illustrates that the frame 3, together with thestencil 4, and the squeegee 5 adopt a lower position in which thesqueegee 5 urges the stencil 4 against the print material 6a, while thearrow "K" illustrates that the flat printing table 2 is now in its upperposition, the same position as that shown in FIG. 1, in which itsupports the print material.

It will also be seen that the print material 6 has been transported to alaying-off position, by the gripper 7, the reference 13 illustrating alaying-off table.

As will also be seen from FIG. 5, a registered gripper 12 now grips newprint-material 6b located in the laying-on station and intended forprint.

Finally, FIG. 6 illustrates that during an actual printing sequence, thegripper 8, the print-material 6a, the table 2 and the frame 3 are movedin unison, i.e. together, to the left, while maintaining registrationbetween gripper 8 and the table 2, at the same time as the squeegee 5 ismoved horizontally to the right in the direction of the arrow "A". Theprinting speed is the sum of these movements.

It should be noted in particular that during the time period in whichthe frame 3 and the printing table 2 are displaced from the positionillustrated in FIG. 3 to the position illustrated in FIG. 4, at the sametime as the squeegee is moved from the position shown in FIG. 3 to theposition shown in FIG. 4, the gripper 8 will move the print material 6afrom the FIG. 3 position to the FIG. 4 position, which means thatmovement of the gripper 8 and the print material 6a will take place at agreater speed from the FIG. 3 position to the FIG. 4 position than theevents occurring during the printing sequence in FIG. 6. Thus, theendless movement-transmission means shall be capable of being driven atmutually different speeds at mutually different times, determined by thepositions of the frame and the table 2.

FIG. 7 illustrates a modified embodiment, in which the grippers 7', 8'can be raised and lowered by means of a link-arm arrangment 15, 16, andin which the endless movement-transmission means 10' has a slightlymodified configuration than the movement-transmission means describedwith reference to FIGS. 1-6.

It will be obvious that the printing table 2 is stationary relative tothe stand and that movement of the gripper 8' takes place over theprinting table 2 when the frame 3 is in its upper position, illustratedin FIG. 3. This will ensure that a sufficiently large space is obtainedbetween the frame 3 and the uppermost surface of the printing table 2,so as to enable the gripper 8 with print material 6a held thereby topass over the printing table 2.

The operational state illustrated in FIG. 7 corresponds to theoperational state illustrated in FIG. 1. It is evident that theembodiment illustrated in FIG. 7 can take positions which conform to thepositions illustrated in FIGS. 2-5, and also in FIG. 6, although suchpositions are not shown, since they are considered to be obvious.

Thus, in the case of both embodiments, the printing table comprises aflat printing-table 2 which can be moved reciprocatingly in synchronismwith the frame 3, and that during a printing sequence a gripper 8operative to collect print material 6a from the laying-on station isregistered in the printing table for common movement therewith.

Furthermore, the squeegee 5, during a printing sequence, is arranged tomove in relation to the stencil at twice the speed that it movesrelative to the stand 9 of the printer. Furthermore, the grippers arerelated to one another via endless movement-transmission means (chains)and are moved intermittently, via machinery not shown. This enablessimultaneous registration of a first gripper in the laying-on stationand registration of a second gripper in the printing table, when saidtable is raised to its upper position or the gripper is lowered to itslower position. The gripper may conveniently be provided with pinsintended for coaction with holes in the printing table.

The movement path of the squeegee in relation to the printer stand andthe movement path of the frame relative to said stand are mutually equaland adapted to the length extension of the print pattern in thetransport direction.

A silk screen printer provided with a raisable and lowerable gripper isdescribed and illustrated in European Patent Specification 0 109 598.

A silk screen printer having a raisable and lowerable printing table isillustrated and described in U.S. Pat. No. 3,384,010.

It will be understood that the invention is not restricted to theaforedescribed exemplifying embodiments thereof and that modificationscan be made within the scope of the following claims.

What is claimed is:
 1. A silk screen printer comprising a printingtable, a stencil held in a frame, a squeegee, a gripper for grippingprint material in a laying-on station, and means for moving thesqueegee, the printing table, the frame and the gripper, said squeegeebeing movable relative to the frame to transfer a first pattern on thestencil to print material registered on the printing table to form asecond pattern, said squeegee being movable over the stencil andrelative to the frame in a first direction during an actual printingsequence, whereas the stencil and frame are arranged to move in a seconddirection opposite to said first direction, the printing table being aflat printing-table which is arranged to move reciprocatingly insynchronism with the frame, and in that during a printing sequence thegripper is registered relative to the printing table for movement incommon therewith.
 2. An arrangement according to claim 1, wherein theprinting table can be raised and lowered, and is intended to take anupper position during a printing sequence.
 3. An arrangement accordingto claim 1, wherein the gripper can be raised and lowered, and isintended to take an upper position when print material passes over theprinting table to a position in which the material and gripper areregistered for printing.
 4. An arrangement according to claim 1, whereinthe squeegee is arranged to move, during a printing sequence, at twicethe speed in relation to the stencil than in relation to a stand forminga part of the printer.
 5. An arrangement according to claim 1, includinga plurality of grippers related to one another via endlessmovement-transmission means, said transmission means functioning to moveintermittently so as to afford simultaneous registration of a firstgripper in the laying-on station and registration of a second gripper inrelation to the printing table.
 6. An arrangement according to claim 1,wherein a movement path of the squeegee relative to a stand forming apart of the printer and a movement path of the frame relative to thestand are mutually equal, the sum of said movement paths being adaptedto the length extension of the printed patter in the transportdirection.
 7. An arrangement according to claim 2, including a pluralityof grippers related to one another via endless movement-transmissionmeans, said transmission means functioning to move intermittently so asto afford simultaneous registration of a first gripper in the laying-onstation and registration of a second gripper in relation to the printingtable.
 8. An arrangement according to claim 4, wherein a movement pathof the squeegee relative to a stand forming a part of the printer and amovement path of the frame relative to the stand are mutually equal, thesum of said movement paths being adapted to the length extension of theprinted pattern in the transport direction.